:root {
    --primary-color: #2563eb;
    --primary-dark: #1e40af;
    --secondary-color: #64748b;
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --bg-primary: #ffffff;
    --bg-secondary: #f8fafc;
    --bg-tertiary: #f1f5f9;
    --border-color: #e2e8f0;
    --shadow-sm: 0 1px 2px 0 rgb(0 0 0 / 0.05);
    --shadow-md: 0 4px 6px -1px rgb(0 0 0 / 0.1);
    --shadow-lg: 0 10px 15px -3px rgb(0 0 0 / 0.1);
    --transition: all 0.3s ease;
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    line-height: 1.6;
    color: var(--text-primary);
    background-color: var(--bg-primary);
    font-size: 16px;
}

/* Navigation */
.navbar {
    position: sticky;
    top: 0;
    background-color: rgba(255, 255, 255, 0.95);
    backdrop-filter: blur(10px);
    border-bottom: 1px solid var(--border-color);
    z-index: 1000;
    padding: 1rem 0;
}

.nav-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.nav-logo {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--primary-color);
}

.nav-menu {
    display: flex;
    list-style: none;
    gap: 2rem;
}

.nav-menu a {
    text-decoration: none;
    color: var(--text-secondary);
    font-weight: 500;
    transition: var(--transition);
    position: relative;
}

.nav-menu a:hover {
    color: var(--primary-color);
}

.nav-menu a::after {
    content: '';
    position: absolute;
    bottom: -5px;
    left: 0;
    width: 0;
    height: 2px;
    background-color: var(--primary-color);
    transition: var(--transition);
}

.nav-menu a:hover::after {
    width: 100%;
}

/* Hero Section */
.hero {
    background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
    color: white;
    padding: 6rem 2rem;
    text-align: center;
}

.hero-container {
    max-width: 1200px;
    margin: 0 auto;
}

.hero-profile {
    margin-bottom: 2rem;
    display: flex;
    justify-content: center;
    animation: fadeInDown 0.8s ease;
    width: 120px;
    height: 120px;
    margin-left: auto;
    margin-right: auto;
    border-radius: 50%;
    overflow: hidden;
}

.profile-image {
    width: 120px !important;
    height: 120px !important;
    min-width: 120px;
    min-height: 120px;
    max-width: 120px;
    max-height: 120px;
    border-radius: 50% !important;
    object-fit: cover;
    object-position: center;
    border: 4px solid rgba(255, 255, 255, 0.3);
    box-shadow: 0 10px 30px rgba(0, 0, 0, 0.3);
    transition: var(--transition);
    display: block;
    overflow: hidden;
}

.profile-image:hover {
    transform: scale(1.05);
    box-shadow: 0 15px 40px rgba(0, 0, 0, 0.4);
}

@keyframes fadeInDown {
    from {
        opacity: 0;
        transform: translateY(-20px);
    }
    to {
        opacity: 1;
        transform: translateY(0);
    }
}

.hero-name {
    font-size: 3.5rem;
    font-weight: 700;
    margin-bottom: 0.5rem;
    letter-spacing: -0.02em;
}

.hero-title {
    font-size: 1.5rem;
    font-weight: 500;
    margin-bottom: 0.5rem;
    opacity: 0.95;
}

.hero-subtitle {
    font-size: 1.125rem;
    margin-bottom: 2rem;
    opacity: 0.9;
}

.hero-contact {
    display: flex;
    justify-content: center;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
}

.contact-link {
    color: white;
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
    opacity: 0.95;
}

.contact-link:hover {
    opacity: 1;
    text-decoration: underline;
}

.separator {
    opacity: 0.7;
}

/* Main Content */
.main-content {
    max-width: 1200px;
    margin: 0 auto;
    padding: 4rem 2rem;
}

.section {
    margin-bottom: 4rem;
    scroll-margin-top: 100px;
}

.section-title {
    font-size: 2rem;
    font-weight: 700;
    color: var(--text-primary);
    margin-bottom: 2rem;
    padding-bottom: 0.5rem;
    border-bottom: 3px solid var(--primary-color);
    display: inline-block;
}

.section-content {
    margin-top: 2rem;
}

/* Timeline Items */
.timeline-item {
    margin-bottom: 3rem;
    padding-left: 2rem;
    border-left: 3px solid var(--border-color);
    position: relative;
}

.timeline-item::before {
    content: '';
    position: absolute;
    left: -8px;
    top: 0;
    width: 13px;
    height: 13px;
    border-radius: 50%;
    background-color: var(--primary-color);
    border: 3px solid var(--bg-primary);
}

.timeline-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    flex-wrap: wrap;
    gap: 1rem;
    margin-bottom: 0.5rem;
}

.timeline-title {
    font-size: 1.25rem;
    font-weight: 600;
    color: var(--text-primary);
}

.timeline-date {
    color: var(--primary-color);
    font-weight: 600;
    white-space: nowrap;
}

.timeline-location,
.timeline-role {
    color: var(--text-secondary);
    font-style: italic;
    margin-bottom: 0.5rem;
}

.timeline-degree {
    font-weight: 500;
    margin-bottom: 0.5rem;
}

.timeline-description {
    color: var(--text-secondary);
    margin-top: 0.5rem;
}

.timeline-stats {
    margin: 1rem 0;
}

.timeline-stats p {
    margin: 0.25rem 0;
    color: var(--text-secondary);
}

.timeline-honors {
    margin: 1rem 0;
    color: var(--text-secondary);
}

.timeline-list {
    list-style: none;
    padding-left: 0;
    margin-top: 0.5rem;
}

.timeline-list li {
    padding-left: 1.5rem;
    position: relative;
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
}

.timeline-list li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
}

.coursework,
.academic-leaves {
    margin-top: 1rem;
}

.coursework ul,
.academic-leaves ul {
    list-style: none;
    padding-left: 1.5rem;
    margin-top: 0.5rem;
}

.coursework li,
.academic-leaves li {
    padding-left: 1rem;
    position: relative;
    margin-bottom: 0.25rem;
    color: var(--text-secondary);
}

.coursework li::before,
.academic-leaves li::before {
    content: '•';
    position: absolute;
    left: 0;
    color: var(--primary-color);
}

/* Project Cards */
.project-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 1.5rem;
    transition: var(--transition);
}

.project-card:hover {
    box-shadow: var(--shadow-md);
    transform: translateY(-2px);
}

.project-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    flex-wrap: wrap;
    gap: 1rem;
    margin-bottom: 0.5rem;
}

.project-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
}

.project-date {
    color: var(--text-secondary);
    font-size: 0.9rem;
    white-space: nowrap;
}

.project-role {
    color: var(--primary-color);
    font-weight: 500;
    margin-bottom: 0.5rem;
}

.award-badge {
    display: inline-block;
    background: linear-gradient(135deg, #fbbf24 0%, #f59e0b 100%);
    color: white;
    padding: 0.25rem 0.75rem;
    border-radius: 12px;
    font-size: 0.875rem;
    font-weight: 600;
    margin-left: 0.5rem;
}

.project-list {
    list-style: none;
    padding-left: 0;
    margin-top: 0.5rem;
}

.project-list li {
    padding-left: 1.5rem;
    position: relative;
    margin-bottom: 0.5rem;
    color: var(--text-secondary);
}

.project-list li::before {
    content: '▸';
    position: absolute;
    left: 0;
    color: var(--primary-color);
    font-weight: bold;
}

/* Publications */
.publication-item {
    background: var(--bg-secondary);
    border-left: 4px solid var(--primary-color);
    padding: 1.5rem;
    margin-bottom: 1rem;
    border-radius: 4px;
}

.publication-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.5rem;
}

.publication-venue {
    color: var(--primary-color);
    font-weight: 500;
    margin-bottom: 0.25rem;
}

.publication-authors {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 1rem;
}

.paper-button {
    display: inline-flex;
    align-items: center;
    gap: 0.5rem;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 0.625rem 1.5rem;
    border-radius: 8px;
    text-decoration: none;
    font-weight: 600;
    font-size: 0.95rem;
    transition: var(--transition);
    border: none;
    cursor: pointer;
    box-shadow: var(--shadow-sm);
}

.paper-button:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-lg);
    background: linear-gradient(135deg, var(--primary-dark) 0%, #1e3a8a 100%);
}

.paper-icon {
    transition: var(--transition);
}

.paper-button:hover .paper-icon {
    transform: translate(2px, -2px);
}

/* 데스크톱에서 더 큰 버튼 */
@media (min-width: 769px) {
    .paper-button {
        padding: 0.75rem 2rem;
        font-size: 1rem;
        border-radius: 10px;
    }
    
    .paper-icon {
        width: 18px;
        height: 18px;
    }
}

/* Awards */
.award-item {
    display: flex;
    gap: 2rem;
    margin-bottom: 1.5rem;
    padding-bottom: 1.5rem;
    border-bottom: 1px solid var(--border-color);
}

.award-item:last-child {
    border-bottom: none;
}

.award-date {
    color: var(--primary-color);
    font-weight: 600;
    min-width: 100px;
}

.award-content {
    flex: 1;
}

.award-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.award-org {
    color: var(--text-secondary);
}

/* Skills */
.skills-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
    gap: 1.5rem;
}

.skill-category {
    background: var(--bg-secondary);
    padding: 1.5rem;
    border-radius: 8px;
    border: 1px solid var(--border-color);
}

.skill-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--primary-color);
    margin-bottom: 0.5rem;
}

.skill-category p {
    color: var(--text-secondary);
    line-height: 1.8;
}

/* Leadership */
.leadership-item {
    margin-bottom: 2rem;
    padding-bottom: 2rem;
    border-bottom: 1px solid var(--border-color);
}

.leadership-item:last-child {
    border-bottom: none;
}

.leadership-title {
    font-size: 1.125rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 0.25rem;
}

.leadership-org {
    color: var(--text-secondary);
    margin-bottom: 0.5rem;
}

.leadership-date {
    color: var(--primary-color);
    font-weight: 500;
    display: block;
    margin-bottom: 0.5rem;
}

.leadership-desc {
    color: var(--text-secondary);
    margin-top: 0.5rem;
}

/* Interests */
.interests-list {
    display: flex;
    flex-wrap: wrap;
    gap: 1rem;
}

.interest-tag {
    display: inline-block;
    background: linear-gradient(135deg, var(--primary-color) 0%, var(--primary-dark) 100%);
    color: white;
    padding: 0.5rem 1.25rem;
    border-radius: 20px;
    font-weight: 500;
    font-size: 0.95rem;
    transition: var(--transition);
}

.interest-tag:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-md);
}

/* Footer */
.footer {
    background: var(--bg-tertiary);
    border-top: 1px solid var(--border-color);
    padding: 2rem 0;
    margin-top: 4rem;
}

.footer-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: 0 2rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 1rem;
}

.footer-links {
    display: flex;
    gap: 1.5rem;
}

.footer-links a {
    color: var(--text-secondary);
    text-decoration: none;
    font-weight: 500;
    transition: var(--transition);
}

.footer-links a:hover {
    color: var(--primary-color);
}

.visitor-stats {
    text-align: center;
    margin-top: 1rem;
    font-size: 0.75rem;
    color: var(--text-secondary);
    opacity: 0.7;
}

.visitor-separator {
    margin: 0 0.5rem;
    opacity: 0.5;
}

/* About Section */
.about-text {
    font-size: 1.125rem;
    line-height: 1.8;
    color: var(--text-secondary);
    max-width: 800px;
}

/* Responsive Design */
@media (max-width: 768px) {
    .navbar {
        position: static;
    }

    .nav-menu {
        flex-direction: column;
        gap: 0.5rem;
    }

    .hero-profile {
        width: 100px;
        height: 100px;
    }

    .profile-image {
        width: 100px !important;
        height: 100px !important;
        min-width: 100px !important;
        min-height: 100px !important;
        max-width: 100px !important;
        max-height: 100px !important;
    }

    .hero-name {
        font-size: 2.5rem;
    }

    .hero-title {
        font-size: 1.25rem;
    }

    .hero-subtitle {
        font-size: 1rem;
    }

    .hero-contact {
        flex-direction: column;
        gap: 0.5rem;
    }

    .separator {
        display: none;
    }

    .main-content {
        padding: 2rem 1rem;
    }

    .section-title {
        font-size: 1.5rem;
    }

    .timeline-header {
        flex-direction: column;
    }

    .project-header {
        flex-direction: column;
    }

    .award-item {
        flex-direction: column;
        gap: 0.5rem;
    }

    .skills-grid {
        grid-template-columns: 1fr;
    }

    .footer-container {
        flex-direction: column;
        text-align: center;
    }
}

@media (max-width: 480px) {
    .hero {
        padding: 4rem 1rem;
    }

    .hero-profile {
        width: 80px;
        height: 80px;
    }

    .profile-image {
        width: 80px !important;
        height: 80px !important;
        min-width: 80px !important;
        min-height: 80px !important;
        max-width: 80px !important;
        max-height: 80px !important;
    }

    .hero-name {
        font-size: 2rem;
    }

    .nav-container {
        padding: 0 1rem;
    }

    .main-content {
        padding: 2rem 0.5rem;
    }
}

/* Smooth Scrolling */
html {
    scroll-behavior: smooth;
}